The present invention relates generally to signal transmission in non-contacting interfaces and more particularly to power and information transfer in non-contacting interfaces.
Many systems require power and/or information to be transferred between surfaces in motion, such as between rotating surfaces. Generally, this is accomplished using contacting or non-contacting slip rings (e.g., rotary transformers, rotary electrical interfaces, rotating electrical connectors, collectors, swivels, electrical rotary joints, etc.). The slip ring system couples electrical signals between two portions of the slip ring that rotate in relation to each other.
A contact-type slip ring generally consists of a conductive circle or band mounted on a shaft and insulated from it. The rotating portion of the system, such as the rotor of a generator, is electrically connected to the conductive circle. Fixed contacts or brushes run in contact with the conductive circle, transferring electrical power or signals to the static portion of the system.
Contact-type slip rings have numerous disadvantages including mechanical failure, sparking, noise introduction, limited power and/or data rate transfer capability, etc. Non-contacting slip rings have been employed to overcome some of the disadvantages introduced by contact-type slip ring systems.
Non-contacting slip ring systems have employed various means for transmitting information across a small gap between the rotating and the non-rotating portions of the slip ring systems. For example, U.S. Pat. No. 6,452,668, entitled “Rotating head optical transmitter for position measurement system,” U.S. Pat. No. 6,630,993, entitled “Method and optical receiver with easy setup means for use in position measurement systems,” U.S. Pat. No. 6,870,608, entitled “Versatile transmitter and receiver for position measurement,” and U.S. Pat. No. 7,187,823, entitled “Contact-free slip ring for survey instrumentation” describe various uses of optical transmitters to transmit information across an air gap between the rotating and the non-rotating portions of the slip ring systems. Such systems require highly precise alignment (e.g., micron level alignment) to ensure proper signal transmission. These systems therefore require manufacturing and alignment tolerances that are difficult to achieve in order to function properly.
Accordingly, improved systems and methods for data and/or power transmission in contact free slip rings are required.